•  681
    Contractions of noncontractive consequence relations
    Review of Symbolic Logic 8 (3): 506-528. 2015.
    Some theorists have developed formal approaches to truth that depend on counterexamples to the structural rules of contraction. Here, we study such approaches, with an eye to helping them respond to a certain kind of objection. We define a contractive relative of each noncontractive relation, for use in responding to the objection in question, and we explore one example: the contractive relative of multiplicative-additive affine logic with transparent truth, or MAALT.
  •  630
    Williamson on Counterpossibles
    Journal of Philosophical Logic 47 (4): 693-713. 2018.
    A counterpossible conditional is a counterfactual with an impossible antecedent. Common sense delivers the view that some such conditionals are true, and some are false. In recent publications, Timothy Williamson has defended the view that all are true. In this paper we defend the common sense view against Williamson’s objections.
  •  92
    Classical counterpossibles
    with Patrick Girard and David Ripley
    Review of Symbolic Logic 15 (1): 259-275. 2022.
    We present four classical theories of counterpossibles that combine modalities and counterfactuals. Two theories are anti-vacuist and forbid vacuously true counterfactuals, two are quasi-vacuist and allow counterfactuals to be vacuously true when their antecedent is not only impossible, but also inconceivable. The theories vary on how they restrict the interaction of modalities and counterfactuals. We provide a logical cartography with precise acceptable boundaries, illustrating to what extent n…Read more
  •  87
    Notational Variance and Its Variants
    Topoi 38 (2): 321-331. 2019.
    What does it take for two logics to be mere notational variants? The present paper proposes a variety of different ways of cashing out notational variance, in particular isolating a constraint on any reasonable account of notational variance which makes plausible that the only kinds of translations which can witness notational variance are what are sometimes called definitional translations.
  •  86
    Structural Reflexivity and the Paradoxes of Self-Reference
    Ergo: An Open Access Journal of Philosophy 3. 2016.
  •  71
    An Argument for the Ontological Innocence of Mereology
    Erkenntnis 81 (4): 683-704. 2016.
    In Parts of Classes David Lewis argued that mereology is ‘ontologically innocent’, mereological notions not incurring additional ontological commitments. Unfortunately, though, Lewis’s argument for this is not fully spelled out. Here we use some formal results concerning translations between formal languages to argue for the ontological innocence of mereology directly.
  •  66
    An Argument Against General Validity?
    Thought: A Journal of Philosophy 1 (1): 4-9. 2012.
    This paper argues that a prominent—and oft-thought to be persuasive—argument against general validity as the best account of validity for languages containing the actuality operator is flawed, the flaw arising out of inadequate attention to the formalisation of mood distinctions
  •  56
    Expressive power, mood, and actuality
    Synthese 190 (9): 1689-1699. 2013.
    In Wehmeier (J Philos Log 33:607–630, 2004) we are presented with the subjunctive modal language, a way of dealing with the expressive inadequacy of modal logic by marking atomic predicates as being either in the subjunctive or indicative mood. Wehmeier claims that this language is expressively equivalent to the standard actuality language, and that despite this the marked-unmarked dichotomies are not the same in the two languages. In this paper we will attend to Wehmeier’s argument that this is…Read more
  •  46
    A simplified embedding of E into monomodal K
    Logic Journal of the IGPL 17 (4): 421-428. 2009.
    In this paper we will provide a modal-to-modal translational embedding of E into K, simplifying a similar result which is obtainable using a novel translation due to S.K. Thomason.
  •  46
    The purpose of the present note is to advertise an interesting conjecture concerning a well-known translation in modal logic, by confirming a (highly restricted) special case of the conjecture.
  •  43
    Metasequents and Tetravaluations
    Journal of Philosophical Logic 51 (6): 1-24. 2021.
    In this paper we treat metasequents—objects which stand to sequents as sequents stand to formulas—as first class logical citizens. To this end we provide a metasequent calculus, a sequent calculus which allows us to directly manipulate metasequents. We show that the various metasequent calculi we consider are sound and complete w.r.t. appropriate classes of tetravaluations where validity is understood locally. Finally we use our metasequent calculus to give direct syntactic proofs of various col…Read more
  •  41
    Paradoxes and structural rules from a dialogical perspective
    with Catarina Dutilh Novaes
    Philosophical Issues 28 (1): 129-158. 2018.
    In recent years, substructural approaches to paradoxes have become quite popular. But whatever restrictions on structural rules we may want to enforce, it is highly desirable that such restrictions be accompanied by independent philosophical motivation, not directly related to paradoxes. Indeed, while these recent developments have shed new light on a number of issues pertaining to paradoxes, it seems that we now have even more open questions than before, in particular two very pressing ones: wh…Read more
  •  37
    A dialogical route to logical pluralism
    Synthese 198 (Suppl 20): 4969-4989. 2019.
    This paper argues that adopting a particular dialogical account of logical consequence quite directly gives rise to an interesting form of logical pluralism, the form of pluralism in question arising out of the requirement that deductive proofs be explanatory.
  •  34
    A Sequent Calculus for Urn Logic
    Journal of Logic, Language and Information 24 (2): 131-147. 2015.
    Approximately speaking, an urn model for first-order logic is a model where the domain of quantification changes depending on the values of variables which have been bound by quantifiers previously. In this paper we introduce a model-changing semantics for urn-models, and then give a sequent calculus for urn logic by introducing formulas which can be read as saying that “after the individuals a1,..., an have been drawn, A is the case”.
  •  32
    We give a simple sequent calculus presentation of R.B. Angell’s logic of analytic containment, recently championed by Kit Fine as a plausible logic of partial content.
  •  28
    A Note on the Logic of Eventual Permanence for Linear Time
    Notre Dame Journal of Formal Logic 49 (2): 137-142. 2008.
    In a paper from the 1980s, Byrd claims that the logic of "eventual permanence" for linear time is KD5. In this note we take up Byrd's novel argument for this and, treating the problem as one concerning translational embeddings, show that rather than KD5 the correct logic of "eventual permanence" is KD45
  •  28
    Valuations: Bi, Tri, and Tetra
    Studia Logica 107 (6): 1313-1346. 2019.
    This paper considers some issues to do with valuational presentations of consequence relations, and the Galois connections between spaces of valuations and spaces of consequence relations. Some of what we present is known, and some even well-known; but much is new. The aim is a systematic overview of a range of results applicable to nonreflexive and nontransitive logics, as well as more familiar logics. We conclude by considering some connectives suggested by this approach.
  •  28
    Denumerably Many Post-Complete Normal Modal Logics with Propositional Constants
    Notre Dame Journal of Formal Logic 53 (4): 549-556. 2012.
    We show that there are denumerably many Post-complete normal modal logics in the language which includes an additional propositional constant. This contrasts with the case when there is no such constant present, for which it is well known that there are only two such logics.
  •  26
    Two traditions in abstract valuational model theory
    Synthese 198 (S22): 5291-5313. 2019.
    We investigate two different broad traditions in the abstract valuational model theory for nontransitive and nonreflexive logics. The first of these traditions makes heavy use of the natural Galois connection between sets of valuations and sets of arguments. The other, originating with work by Grzegorz Malinowski on nonreflexive logics, and best systematized in Blasio et al. : 233–262, 2017), lets sets of arguments determine a more restricted set of valuations. After giving a systematic discussi…Read more
  •  25
    Getting some (non-classical) closure with justification logic
    Asian Journal of Philosophy 2 (2): 1-25. 2023.
    Justification logics provide frameworks for studying the fine structure of evidence and justification. Traditionally, these logics do not impose any closure requirements on justification. In this paper, we argue that for some applications they should subject justification to closure under some variety of logical consequence. Specifically, we argue, building on ideas from Beall, that the non-classical logic FDE offers a particularly attractive notion of consequence for this purpose and define a j…Read more
  •  25
    Valuations: Bi, Tri, and Tetra
    Studia Logica 107 (6): 1313-1346. 2019.
    This paper considers some issues to do with valuational presentations of consequence relations, and the Galois connections between spaces of valuations and spaces of consequence relations. Some of what we present is known, and some even well-known; but much is new. The aim is a systematic overview of a range of results applicable to nonreflexive and nontransitive logics, as well as more familiar logics. We conclude by considering some connectives suggested by this approach.
  •  23
    Our concern here is with the extent to which the expressive equivalence of Wehmeier’s Subjunctive Modal Language and the Actuality Modal Language is sensitive to the choice of background modal logic. In particular we will show that, when we are enriching quantified modal logics weaker than S5, AML is strictly expressively stronger than SML, this result following from general considerations regarding the relationship between operators and predicate markers. This would seem to complicate arguments…Read more
  •  21
    An observation concerning porte's rule in modal logic
    Bulletin of the Section of Logic 44 (1/2): 25-31. 2015.
    It is well known that no consistent normal modal logic contains (as theorems) both ♦A and ♦¬A (for any formula A). Here we observe that this claim can be strengthened to the following: for any formula A, either no consistent normal modal logic contains ♦A, or else no consistent normal modal logic contains ♦¬A.
  •  12
    ABSTRACT In our response Field's ‘Properties, Propositions and Conditionals’, we explore the methodology of Field's program. We begin by contrasting it with a proof-theoretic approach and then commenting on some of the particular choices made in the development of Field's theory. Then, we look at issues of property identity in connection with different notions of equivalence. We close with some comments relating our discussion to Field's response to Restall’s [2010] ‘What Are We to Accept, and W…Read more
  •  8
    Metasequents and Tetravaluations
    Journal of Philosophical Logic 51 (6): 1453-1476. 2022.
    In this paper we treat metasequents—objects which stand to sequents as sequents stand to formulas—as first class logical citizens. To this end we provide a metasequent calculus, a sequent calculus which allows us to directly manipulate metasequents. We show that the various metasequent calculi we consider are sound and complete w.r.t. appropriate classes of tetravaluations where validity is understood locally. Finally we use our metasequent calculus to give direct syntactic proofs of various col…Read more
  •  3
    Tolerance and the Bounds
    Análisis Filosófico 41 (2): 303-316. 2021.
    The present note investigates the connection between nonreflexive and nontransitive logics from a bounds-theoretic perspective. What will emerge is one way in which, if we focus on the ways in which strict and tolerant acts constrain one another, nonreflexive and nontransitive notions of consequence can be seen as simply reflecting different aspects of the same underlying reality.